I live in FL where it is very sunny and very warm to hot. We only water
our roses in the morning so that the sun will dry the leaves preventing
most of the fungus. I also never water 'over the top' only underneath
in the 'well' that I encircle each bush with= again FL= sandy soils and
HOT evaporation. Others can explain the fungicide/ food regimen better
than I.
I thought that your planting technique was excellent- I doubt that I'm
that fastidious when I plant each bush!